Although the present invention is described herein with particular reference to television audience monitoring, it should be realized that the present invention applies also to the monitoring of other forms of audience entertainment, such as to the monitoring of radio audiences. Moreover, as used herein, the term “programs” means segments of various lengths such as all or parts of programs, commercials, promos, public service announcements, and so on.
Broadcast audience measurements have conventionally been made with equipment placed in statistically selected households to monitor the channels to which each receiver in the statistically selected households is tuned. Currently, data from such statistically selected households are collected at a central office and compared with separately collected reference data. This reference data includes a compiled list of those programs which are available on each receivable channel during each time period of interest, and are commonly referred to as program records. (Reference data may alternatively be referred to as station records, cable records, or the like.) By comparing the tuned channels, i.e. the channels to which the receivers in the statistically selected household were tuned, to the programs available on those channels at the time, an inference can be made as to the identities of the programs selected by the members of the household.
Conventional audience measurement equipment is expensive to install in a statistically selected household. A significant part of this expense is associated with the need to calibrate the tuned channels to the corresponding program sources (especially when the signals that come into the household are routed through a multitude of tuners, such as television tuners, cable converters, VCR tuners, and the like). Another significant part of this expense arises from the common need to open up (i.e., intrude into) monitored receivers and/or associated equipment so that the installer of the audience measurement equipment can secure access to the tuners of these receivers and/or associated equipment. Also, members of the statistically selected households may be reluctant to permit such intrusions for fear that the intrusions will cause damage or be unsightly.
Moreover, there is always at least some inherent confusion in the viewing records produced by an audience measurement system because, although the system accurately reports both the channels to which the receivers in a statistically selected household are tuned and the times during which those receivers are tuned to those channels, the programs currently being broadcast on those channels and at those times are not always accurately known. One suggested approach to avoiding this confusion is to label each broadcast program with an ancillary code (e.g., a digital code written on a selected video line in the vertical blanking interval of each video program to be broadcasted and/or monitored). This ancillary code can then be read by the metering equipment in the sampled households and can be compared (e.g., in a central office computer) to the ancillary codes stored in a code-program name library. The code-program name library contains a manually entered list of program names and the ancillary codes associated therewith. Thus, given an ancillary code of a program selected for viewing and/or listening in the sampled households, the program name of this program can be easily determined from the library. Such a system, however, has not been successfully employed in statistically selected households for audience measurement because it requires all possible programs to be encoded before a complete measurement can be made, and because it requires an ancillary code that can pass through a variety of distribution and broadcasting processes without being stripped or corrupted and thereby rendered illegible.
Therefore, instead of reading ancillary codes in statistically selected households in order to identify the programs to which receivers are tuned, ancillary codes are read in each market area in order to instead verify the program records. That is, the typical audience measurement system determines both the channels to which the receivers in the statistically selected households are tuned and the times that the receivers are tuned to those channels. The tuned channels, and the times during which those channels are tuned, are periodically transmitted to a central facility where the tuned channels, and the times during which those channels are tuned, are compared to the aforementioned program record. This program record is compiled from information supplied by the sources of these programs, and is intended to reflect the identity of the programs which are supposed to be aired at the times indicated in the program records. Current systems which read the ancillary codes of these programs are used simply to verify the accuracy of the program records, i.e. to verify that the programs were actually aired at the intended times and on the intended channels as indicated in the program records. Accordingly, even though not all programs are labelled with ancillary codes, some are. These ancillary codes are read in order to verify that at least those programs, which contain ancillary codes, were aired at the intended times and on the intended channels.
An example of such a system is disclosed by Haselwood, et al. in U.S. Pat. No. 4,025,851, which is assigned to the same assignee as the current application. The system disclosed therein monitors those programs which have an ancillary code written on a video line of one or more of a video program's vertical blanking intervals. The system described in this patent, which is generally referred to as the Automated Monitoring of Line-up (AMOL) system, has been in general use in the United States for over a decade, and is used to determine (i) the identity of aired programs, (ii) the local stations which air these programs, and (iii) the times during which these programs are aired. A system of this type significantly reduces the complexity, and improves the accuracy, of the resulting program records that are an essential element of current national television audience measurements. The AMOL system has not been used heretofore within statistically sampled households due to intrusive installations of metering equipment, code loss error problems, and lack of codes in some programs all of which can be more successfully remedied at a central monitoring site, but that are intractable in sampled households.
Other code monitoring systems include the radio audience monitoring system disclosed by Weinblatt in U.S. Pat. No. 4,718,106. Weinblatt teaches an audience measurement system in which each participant wears a metering device that includes a microphone and a detection circuit which responds to in-band codes in the programming. Weinblatt discusses background noise as a problem in this method, and teaches that such noise is avoidable by using a microphone having a low sensitivity. The system disclosed in U.S. Pat. No. 4,807,031 utilizes a robust video luminance coding method with a low data rate. The system disclosed in U.S. Pat. No. 4,945,412 utilizes a sub-audible 40 Hz tone to encode the audio portion of a broadcast.
In U.S. patent application Ser. No. 07/981,199, (now U.S. Pat. No. 5,425,100), which is assigned to the same assignee as the current application, Thomas et al teach a multi-level encoding system in which an ancillary code may be inserted into a program at each level of distribution of the program. Each ancillary code identifies the source in its corresponding level of the multi-level encoding system. Thus, the program may be tracked through the distribution system.
As discussed above, systems which rely upon encoded broadcasts to identify programs require that all programs be encoded by at least one of the program sources (e.g., broadcasters) in the distribution system. Even in the unlikely event that all broadcasters were to agree to cooperate, occasional encoding equipment failures would likely cause gaps in the data provided by systems that rely solely on ancillary codes. These gaps would cause losses of rating data and would render all of the program share measurements is meaningless whenever any significant number of programs are not encoded. Thus, there is a need to collect program identifying data even when there is no ancillary code present in the programs to be identified.
Furthermore, several broadcast measurement systems have been suggested which do not detect embedded ancillary codes in order to identify programs, but which instead monitor program content. These systems generally receive programs to be monitored at a measurement site, extract broadcast signatures from the programs, and compare these broadcast signatures with corresponding reference signatures which have been extracted from previous broadcasts of the programs to be monitored or from reference copies of these programs (e.g., distribution tapes) and which are stored in a reference library. For example, in U.S. Pat. No. 4,697,209, which is assigned to the same assignee as the current application, a program monitoring system is disclosed in which broadcast signatures are collected in sampled households relative to certain program content (e.g., a scene change in the video portion of a monitored program). These broadcast signatures are subsequently compared to reference signatures collected by reference equipment tuned to broadcast sources available in the selected market. A favorable comparison between broadcast signatures and corresponding reference signatures indicates the programs, not just the channels, being viewed. A similar program monitoring system is disclosed in U.S. Pat. No. 4,677,466, which is assigned to the same assignee as the current application and which logs the broadcasts of selected programs (e.g., commercial advertisements).
There are several problems with monitoring equipment which uses extracted signatures in order to identify programs. For example, in order for monitoring equipment to extract useful signatures which can be successfully correlated, the monitoring equipment is necessarily complex if there are too many programs or stations (e.g., more than several hundred) to be monitored. Additionally, such systems rely on reference measurement sites that collect reference signatures from known program sources. When one set of reference equipment fails, all reference signature data for that program source may be lost. Therefore, a redundant backup reference system must be installed. Such systems then become computationally expensive, and their use has been restricted by the cost of computer hardware. Also, in those systems which extract broadcast signatures at a monitoring site and transmit the broadcast signatures to the reference site for correlation with the reference signatures, substantial resources are required in order to process and communicate the broadcast signatures, to transmit these signatures to the reference site, and to compare theses signatures with valid reference signatures. Furthermore, matching signatures must be further processed and compared with program records.
The present invention overcomes one or more of the problems associated with prior art audience measurement systems.